关键词: 古环境分析, 地层划分, 晚第四纪, 钻孔, 福州盆地

Abstract: Fuzhou basin is tectonically located in the eastern part of South China fold system, within the Fuding-Yunxiao Fault depression zone of East Fujian volcanic fault depression zone. It is a fault depression basin developed in the middle and late Quaternary, filled with marine, terrestrial and alternating marine-terrestrial facies sediments with complicated structures. Two test holes(SZK-1 and SZK-2)were drilled in the Gutian Street, Fuzhou City, with the purpose of setting up a standard section of Quaternary strata in Fuzhou basin. The SZK-1 test hole is 56.3m deep, in which the thickness of the Quaternary sediments is 51.1m. From the cores of this borehole, 25 samples were collected for thermoluminescent(TL)dating and 73 samples were collected for sporopollen analysis. The SZK-2 test hole is 53.2m deep, in which the thickness of the Quaternary sediments is 50.9m. From the cores of this test hole 18 samples were collected for TL dating. The distance of these two test holes is 113.5m. Basically, these two boreholes reveal the same features of deposition. The TL dating results of samples from these two test holes show good vertical time sequence and lateral correlation. The relative ages of sediments dated by sporopollen analysis in SZK-1 test hole show a good consistency with the ages dated by TL method. This study has led to some new insights about the sedimentary facies and succession, as well as the paleo-environment of the Fuzhou basin:(1)The sedimentation in Fuzhou basin initiated at middle Epipleistocene, at least at 54.3ka B.P., and terminated after 1ka B.P.(2)The ages of sediments from the two test holes can be assigned to Epipleistocene and Holocene. The Epipleistocene sediments can be subdivided into the sediments of middle and late Epipleistocene, i.e. 54.3ka B.P.～24 ka B.P. and 24 ka B.P.～ 11.3 ka B.P. Moreover, the Holocene sediments include the sediments of early, middle and late Holocene, i.e. 9ka B.P. to later than 1ka B.P.(3)The strata in the two test holes can be divided into three sections. The lower section corresponds to middle Epipleistocene, the middle section to late Epipleistocene, and the upper section to Holocene.(4)The sediments of middle Epipleistocene are composed of celadon gravel, coarse sand and clay, indicating a temperate and dry climate, while the sedimentary facies of the sediments can be assigned to lacustrine and lakeshore facies. The sediments of late Epipleistocene are composed of gray and yellow, coarse and medium sand, indicating a temperate and dry climate, while the sedimentary facies of the sediments can be assigned to fluvial facies. The early Holocene sediments consist of gray medium and coarse sand with a small amount of sludge, indicating a temperate and relatively wet climate, and littoral deposition environment. The middle Holocene sediments are composed of gray interbedded sludge and fine silt, indicating a warm and wet climate, and shallow-sea deposition environment. The late Holocene sediments consist of gray medium-coarse sand, sludge and clay, indicating a transition from littoral, neritic to lacustrine environment, and a warm and wet climate.

Key words: paleoenvironmental analysis, stratigraphic division, late Quaternary, borehole, Fuzhou basin